To fully understand and mitigate global change, we need to understand how species have adapted to past environments and the potential for adaptation to future environmental conditions. Climate change projections indicate that some parts of the midwestern United States will become drier and some will become wetter. Such changes are expected for the many of the world’s species, and for nearly all species living in temperate latitudes. These altered rainfall patterns are a threat to the persistence of many plant species, and in the short-term, plasticity is likely to be an important response to climate change as it allows species’ persistence for a longer period during which adaptation may occur. We do not currently understand if future plant responses to projected climate change can be predicted based on adaptation to past rainfall regimes. To address this issue, we conducted a field experiment where we manipulated precipitation with rainout shelters to investigate how populations of common ragweed (Ambrosia artemisiifolia) adapted to historical rainfall regimes will respond to future rainfall regimes. In replicate plots, I simulated future rainfall regimes using rainout shelters to complete three manipulations: 35% rainfall reduction, 35% rainfall addition, and ambient rainfall. I planted 1300 seeds I collected across a north-south gradient of annual rainfall from MN to LA.
Results/Conclusions
Initial analyses indicate that adaptation to current precipitation is predictive of plastic responses to future precipitation regimes, but these plastic responses may be maladaptive. In the drought treatment, populations originating from northern locales with lower precipitation flowered later and had higher fitness than populations originating from southern locales with higher precipitation, which flowered earlier. Some areas in the southern U.S. are projected to become drier with climate change, therefore these results suggest that adaptation to current precipitation regime and phenotypic plasticity may not mitigate the negative consequences of altered precipitation patterns. This experiment is one of the first to investigate how adaptation to past precipitation will shape performance under future precipitation patterns.